Electron inelastic mean free paths in biological matter based on dielectric theory and local-field corrections

The inelastic mean free path (IMFP) of electrons with energies up to a few keV is calculated from the dielectric electron-gas theory for densities corresponding to those of biological matter. The effect of the many-body local-field correction on the Lindhard dielectric response function is examined using some of the available analytical approximations to its static limit. We have tested the performance of several Hubbard-type local-field corrections along with the formula proposed by Corradini and co-workers [M. Corradini, R. Del Sole, G. Onida, M. Palumno, Phys. Rev. B 57 (1998) 14569] which is extensively used in connection with the exchange-correlation kernel of time-dependent density functional theory. It is shown that the Lindhard dielectric function provides reasonable estimates of electron IMFPs below about 50 eV, where the majority of semi-empirical dielectric calculations based on the extended-optical-data methodology fail. The use of LFC results in a sizeable reduction of the IMFP which, at low energies, may reach ∼20%.